title: Noninvasive identification of materials inside USP vials with Raman spectroscopy and a Raman spectral library.
abstract: A commercial dispersive Raman spectrometer operating at 785 nm with a CCD detector was used to acquire spectra of USP reference materials inside amber USP vials. The laser and collection beams were directed through the bottom of the vials, resulting in a 60% loss of signal. The Raman shift was calibrated with a 4-acetamidophenol standard, and spectral response was corrected with a luminescent standard. After these corrections, the Raman spectra obtained inside the USP vial and on open powders differed by less than 5%. A spectral library of 309 reference materials was constructed, with spectral acquisition times ranging from 1 to 60 s. Of these, 8% had significant fluorescent background but observable Raman features, while 3% showed only fluorescence. A blind test of 26 unknowns revealed the accuracy of the library search to be 88-96%, depending on search algorithm, and 100% if operator discretion was permitted. The tolerance of the library search to degraded signal-to-noise ratio, resolution, and Raman shift accuracy were tested, and the search was very robust. The results demonstrate that Raman spectroscopy provides a rapid, noninvasive technique for compound identification.
authors.affiliation: Ohio State University, Department of Chemistry, Columbus 43210, USA.
authors.forename: R L
authors.initials: RL
authors.lastname: McCreery
authors.forename: A J
authors.initials: AJ
authors.lastname: Horn
authors.forename: J
authors.initials: J
authors.lastname: Spencer
authors.forename: E
authors.initials: E
authors.lastname: Jefferson
mesh_terms: D004349:Drug Packaging; D012015:Reference Standards; D017550:Spectroscopy, Fourier Transform Infrared / Q000592:standards*